Electrofluidynamic accelerator



Apnl 8, 1969 E. G. JOHNSON ELECTRQFLUIDYNAMIC ACCELERATOR Sheet Filed Dec. 23, 1966 INVENTOR. 4 yo Also/v 7ro5sr El IVE/e Z of 2 Sheet Filed Dec. 23, 1966 e r m m M E r 4 V 4W N m m f Y ilnite tat 3,436,960 ELECTROFLUIDYNAMIC ACCELERATOR Elmer G. Johnson, Fairborn, Ohio, assiguor to the United States of America as represented by the Secretary of the Air Force Filed Dec. 23, 1966, Ser. No. 604,484 Int. Cl. Gtllm 9/00 U.S. Cl. 73-147 5 Claims ABSTRACT OF THE DISCLOSURE Prior art There are no prior art devices available for duplicating all the conditions of high-speed flight in the hypersonic range of Mach 15 to Mach 40 in the altitude range of 100,000 feet to 200,000 feet.

The electromagnetic accelerators of the traveling-wave type and the Hall current type and others duplicate these conditions for ultrahigh altitudes of the order of 400,000 feet and higher.

Arc heaters are used to simulate flights in the 100,000 to 200,000 feet range, but when true static temperature is simultated high Mach numbers cannot be attained and when high Mach numbers are attained there is no true static temperature.

Brief description of invention In the device of this invention, energy is added to the gas in the form of kinetic energy by means of an electrostatic acceleration process. Because the corona discharge takes place in a high-pressure chamber, very high accelerating voltages can be used. The electrostatic acceleration process can be used in various types of apparatus, for example, electrical propulsion systems or hypersonic wind tunnels.

The Mach number attainable in this high-speed flight simulation device is limited only by the state of the art in high voltage power supplies. With present state of the art high-voltage power supplied, in the order of 5X10 volts at 10 amps, speed simulation in the Mach to Mach are attainable. Though not now in existence, it is within the knowledge in the art to provide power supplies capable of extending this range to Mach 40 in the altitude range of 100,000 feet to 200,000 feet.

One object of the invention is to provide a system for accelerating a gas to hypersonic velocities with enthalpies corresponding to flight speeds of Mach 12 and higher in an altitude for about 120,000 feet.

Another object is to provide accelerated gases which will more nearly duplicate high-speed flight in a natural atmosphere, than can be obtained by any state of the art device or system.

These and other objects will be more fully understood from the following detailed description taken with the drawing, wherein:

FIG. 1 is a sectional view of an electrofluidynamic accelerator according to one embodiment of the invention;

FIG. 2 is a sectional view of an electrofluidynamic accelerator according to another embodiment of the in vention; and

FIG. 3 is a schematic diagram showing the electrofluidynamic accelerator of FIG. 1 used in a wind tunnel.

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Reference is now made to FIG. 1 of the drawing which shows a high-pressure chamber 10 having a De Laval type nozzle 11 at the input and a divergent nozzle 13 at the output. A heater chamber 15 with heater 16 is provided adjacent nozzle 11. A gas, such as air, at a pressure of the order of 800 atmospheres is supplied to the input 17 of chamber 15 from a high-pressure gas supply 18. A corona discharge electrode 19 is supported within a thick-walled cylinder 20 by means of a plurality of radial leaf supports 22. The cylinder 20 is supported within the chamber 10 by any well-known means such as by the high-voltage power conduit 23. The power conduit is sealed in an insulator 25, which is sealed bet-ween flanges 27 and 28. A high voltage of the order of 5 million volts is supplied through power conduit 23 to the electrode 19 from any well-known power source, for example, as is shown in US. Patent No. 3,225,225 to Wattendorf et al. An insulator gas such as a mixture of nitrogen and carbon dioxide, or any of the other well-known insulator gases, is provided in the chamber 29 within the outer power conduit 30 leading from the high-voltage source 34 to the electrofluidynamic accelerator as shown in FIG. 3. A bypass control valve 31 is provided in chamber 10.

Because of the high stagnation temperature inherent in the electrofluidynamic accelerated gas at the point of impingement of the gas at the throat of nozzle 13, conventional liquid cooling means 32 is provided. It is to be understood that transpiration cooling or injection cooling with a thin layer of cooling gas at the metal surface could be provided, if desired.

In the operation of the device, high-pressure gas of the order of 800 atmospheres is admitted at input 17. The air is heated to a temperature of about 1500 F. by heater 16. The air is then expanded in nozzle 11 to a supersonic velocity of the order of Mach 2. The static pressure within chamber 10 is of the order of atmospheres and the temperature is of the order of 1000 F. The gas is entrained in the corona discharge and accelerated toward nozzle 13 wherein it is expanded to the desired final velocity. The acceleration between electrode 19 and nozzle 13 takes place at a constant pressure. Charged particles within the stream quickly move toward the wall of nozzle 13 and will therefore provide a clean jet of gas in the center of the stream. Also, any contamination that might be present due to bombardment of the nozzle material will only be present in the boundary layer of the air leaving nozzle 13.

While a heater and acceleration nozzle are provided in the device of FIG. 1, gas heated in some other manner could be admitted to input 17 or another means can be used for providing the initial acceleration and heating of the gas for example such as shown in FIG. 2.

In the device of FIG. 2, a high-pressure chamber 34 is connected at ground potential. The expansion nozzle 13' is the same as in FIG. 1. A cylindrical corona discharge electrode 35 is supported in an insulator support 37 sealed between the outer power conduit 38 and the wall of the chamber 34. An insulator gas is provided within the outer power conduit as in the device of FIG. 1. The chamber 34 is shaped to provide a smooth secondary flow. Air at a pressure of the order of 100 atmospheres is supplied at input 40.

In the operation of the device of FIG. 2, high-pressure air is admitted to chamber 34 through inlet 40. The air is entrained in the corona discharge between electrode 35 and nozzle 13'. Because there is some slip in the air, the air will become heated. As the air is accelerated toward nozzle 13, a secondary flow will develop within chamber 34 as indicated by arrows 42. This secondary flow will be heated due to the slip mentioned above. Thus, the secondary air flow will provide the initial acceleration and heat to the air as in the device of FIG. 1.

The use of electrofluidynamic accelerator of FIG. 1 in a hypervelocity flight condition simulator is shown in FIG. 3. In this device, air at about 800 to 1000 atmospheres is taken from the high-pressure storage source 51 by means of a header shown schematically at 52 and is then passed through a heater chamber 15. The heated air is passed a De Laval type nozzle 11 wherein it is accelerated to a velocity of about Mach 2 in chamber 10. The gas is then further accelerated by means of the corona discharge between corona electrode 19 and nozzle 13. The gas is then expanded to a higher velocity in the second nozzle 13, after which it passes through testing chamber 54, wherein the model under test, shown schematically at 55, is located. The gas then passes through a conventional supersonic difiuser 57, a conventional subsonic diifuser 58, cooler 59, and then to a conventional vacuum source 60.

While a single corona discharge electrode is illustrated, it is to be understood that plural electrodes may be employed. Also, it is to be understood that various shapes of electrodes can be used, for eXample, the electrode may be a needle electrode or a cylindrical electrode.

There is thus provided a device for simulating flight conditions in a natural atmosphere.

While certain specific embodiments have been described, it is to be understood that numerous changes may be made without departing from the general principles and scope of the invention.

I claim:

1. An electrofiuidynamic accelerator, comprising: an enclosed chamber; means for supplying a gas at a pressure of the order of 100 atmospheres to said chamber; a divergent nozzle connected at one end of said chamber; a corona discharge electrode Within said chamber; means, including a voltage source of the order of 5X10 volts, for providing a corona discharge between said corona discharge electrode and said divergent nozzle for accelerating said gas toward said divergent nozzle.

2. The device as recited in claim 1 having means, between said high-pressure gas source and said enclosed chamber, for heating the gas, nozzle means between said gas heating means and said enclosed chamber for expanding the gas to a supersonic velocity.

3. The device as recited in claim 1, wherein said enclosed chamber has curved annular walls at the end adjacent said nozzle and the end remote from said nozzle to thereby provide a smooth secondary air flow within said chamber.

4. A device for simulating flight conditions in the 100,000 to 200,000 altitude range, comprising: an enclosed chamber; means for supplying a gas at a pressure of the order of atmospheres to said chamber; a divergent nozzle connected at one end of said chamber; means, including a voltage source of the order of 5 10 volts, for electrostatically accelerating said gas toward said nozzle means; test chamber means, adjacent the output of said nozzle; means, within said test chamber, for supporting a test model within the hypersonic velocity gas stream from said divergent nozzle; vacuum means attached to said flight condition simulating device; supersonic and subsonic diffuser means connected to the output of said test chamber; and gas cooling means between said diffuser means and said vacuum means.

5. The device as recited in claim 4 having means, between said high-pressure gas source and said enclosed chamber, for heating the gas, nozzle means between said gas heating means and said enclosed chamber for expanding the gas to a supersonic velocity.

References Cited UNITED STATES PATENTS 2,995,035 8/1961 Bloxsom et al. 73147 3,035,439 5/1962 Johnson 73-147 3,045,481 7/1962 Bunt et al. 73147 3,066,528 12/1962 Giannini et al 73--147 3,077,108 2/1963 Gage et al. 73-147 3,225,589 12/1965 Spangler et al. 73147 XR 3,238,345 3/1966 Clark et al. 2,765,975 10/ 1956 Lindenblod.

LOUIS R. PRINCE, Primary Examiner.

I. NOLTON, Assistant Examiner. 

